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Myoglobin is a protein located primarily in the striated muscles of vertebrates. MB is the gene encoding myoglobin in humans. It encodes a single polypeptide chain with one oxygen binding site. Myoglobin contains a heme prosthetic group that can reversibly bind to oxygen. The body uses it as an oxygen storage protein in muscle. It is able to bind and release oxygen depending on the oxygen concentration in the cell. Its primary function, as a result, is to supply oxygen to myocytes. Myoglobin also functions in the hemostasis of nitric oxide. It additionally plays a role in the detoxification of reactive oxygen species. Myoglobin is the reason for the red color of the muscle of most vertebrates.[1][2]

Myoglobin knockout models have been created to try to understand its functions more clearly. Mice models have mutated myoglobin to the point of it being undetectable in cardiac and skeletal muscle. The mutation causes several lethal cardiovascular defects in embryos. However, the mice who survived that stage of development exhibited cellular and molecular adaptive responses to deal with the lack of myoglobin. These included having a higher capillary density in the heart to enhance oxygen supply. Their results, along with other similar studies, suggest that although compensatory responses exist, myoglobin is necessary for normal muscle development and function.[9] Myoglobin also plays a role in the pathophysiology of rhabdomyolysis. The process begins with injury to the myocyte membrane or altered energy production; this leads to an influx of extracellular calcium from along with a release of calcium from the sarcoplasmic reticulum and mitochondria from inside of the cell.  The accumulation of excess intracellular calcium causes destructive processes leading to lysis of the cell and release of its contents, including myoglobin. This protein is the primary constituent of muscle that contributes to renal damage. The first proposed mechanism of its toxicity is tubular obstruction. Myoglobin can precipitate out of solution in the renal tubules. This is exacerbated by intravascular volume depletion and acidosis. The second mechanism is by oxidant injury. Iron in myoglobin can dissociate and lead to the release of free radicals and oxidative damage to the renal parenchyma. The final mechanism is by myoglobin inducing lipid peroxidation. This process creates molecules that act as vasoconstrictors to the renal arterioles.[10]